Assembly jig



2 l 9- 1 Z 1 a Aug. 29, 1967 P. BERG ETAL 3,337,942

ASSEMBLY JIG Filed Aug. 30, 1965 2 Sheets-Sheet 1 29, 1967 P. BERG ETAL 3,337,942

ASSEMBLY JIG Filed Aug. 30, 1965 2 Sheets-Sheet 2 United States Patent 3,337,942 ASSEMBLY JIG Philip Berg, Seneca Falls, Glen A. Burdick, Waterloo,

and Alan T. Kuryla, Geneva, N.Y., assignors to Sylvania Electric Products Inc., a corporation of Delaware Filed Aug. 30, 1965, Ser. No. 483,631 7 Claims. (Cl. 29-203) ABSTRACT OF THE DISCLOSURE A cathode-G assembling and spacing jig having cathode holding means and spaced, parallelly aligned cathode spacing rods formed to butt against a preselected stop means. The length difference between the cathode holding means and the cathode spacing means determines the cathode-G spacing.

This invention relates to assembly jigs and more particularly to jigs for assembling and properly spacing a cathode relative to a grid in a cathode ray tube electron gun mount.

Electron gun mounts for cathode ray tubes of the type used with television receivers comprise one or more electron guns each of which comprises a plurality of spaced apart, axially aligned grid electrodes and a cathode. The cathode has an electron emissive material on a surface thereof for providing a beam of electrons and the grid electrodes, usually designated G G G and G respectively, perform the functions of controlling, forming, focussing and accelerating the beam. The various electrodes are maintained in position by radially disposed studs which project therefrom and are fused into glass insulating rods.

The cathodc-to-grid spacing is a critical one in that it determines the cut-off voltage of the tube. It is necessary, therefore, to the scheme of mass production and interchange ability of these tubes that close tolerances be maintained in regard to this spacing and the resultant cut-off voltage dependent thereon.

There are several methods of controlling this spacing currently in use and enjoying varying degrees of success. One of these prior methods utilizes a cup-shaped control grid which has mounted therein a cathode assembly. This assembly usually comprises a substantially cylindrical cathode sleeve, closed at one end, which is mounted in a ceramic disc. The closed end of the cathode sleeve has thereon an emissive material and it is located at a known height above the disc. A cylindrical spacer is affixed to the inside of the control grid and the cathode assembly is positioned within the grid so that the spacer abuts the ceramic disc. A retainer ring is usually positioned against the opposite surface of the ceramic disc and welded to the control grid.

In actual use spacing tolerances are difiicult to maintain with this method. The number of pieces involved and the number of placement operations allows a buildup of error that frequently results in a rejected tube.

A second method employs an air comparator and utilizes a ceramic disc having a cathode receiving eyelet afiixed thereto. The disc and eyelet are positioned in the control grid and mounted therein by any suitable means. The air comparator is then coupled to the closed end of the grid cup by suitable means, as an O-ring seal, and a quantity of air is forced through the beam aperture therein. A cathode sleeve is inserted into the eyelet and advanced toward the closed end of the grid cup until the air flow between the grid and cathode reaches a given level, as indicated on a meter, which indicates a desired spacing. Thereupon, the cathode is welded to the eyelet.

3,337,942 Patented Aug. 29, 1967 There are several disadvantages to this method. It is time consuming and therefore expensive and it necessitates the cathode being assembled within the control grid before the gun is assembled; a requirement that it is often desirable to avoid.

A third method utilized is one similar to that described above but instead of measuring air How the capacitance between the screen grid or G and cathode is measured. This method requires expensive and delicate measuring apparatus and extensive shielding since the cathode-toscreen grid capacitance is of the order of a few femto farads (10 It is an object of this invention, therefore, to enhance the assembly techniques utilized in the manufacture of electron gun mounts.

It is another object of the invention to improve electron gun mounts.

Still another object of the invention is to reduce the assembly time of electron gun mounts with a consequent reduction in cost.

These and other objects are achieved in one aspect of the invention by the provision of an assembly jig comprised of cathode engaging means, cathode spacing means spaced from the cathode engaging means and stop means formed to engage the spacing means. A jig of this type is simple and economical to manufacture and easy to use. It provides solid mechanical stopping action and a consistency of tolerance and spacing heretofore unobtainable.

For a better understanding of the present invention, together with other and further objects, advantages, and capabilities thereof, reference is made to the following disclosure and appended claims in connection with the accompanying drawings in which:

FIG. 1 is an exploded perspective view illustrating one embodiment of the invention;

FIG. 2 is a partial longitudinal sectional view of the apparatus of FIG. 1;

FIG. 3 is a view similar to FIG. 2 illustrating another embodiment of the invention;

FIG. 4 is a view similar to FIG. 3 illustrating another embodiment of the invention; and

FIG. 5 is a view similar to FIG. 4 illustrating still another embodiment of the invention.

Referring now to the drawings with greater particularity, in FIG. 1 there is shown an electron gun mount 10. While in this instance mount 10 is comprised of a single electron gun it is to be noted that the invention is not restricted thereto but includes mounts having more than one gun, such as those used in some types of cathode ray tubes for color television reception. Mount 10 comprises a plurality of grid electrodes designated, respectively, G G G and G a cathode 12, cathode receiving eyelet 14 and eyelet support 16. The grid electrodes and the eyelet support 16 are formed to provide radially disposed studs 18 which project therefrom and are fused into glass insulating rods 20. Cathode receiving eyelet 14 is mounted in an aperture in eyelet support 16 and is firmly alfixed to the support by any suitable means, such as welding.

The assembly jig 22 comprises cathode engaging means 24, which in this instance is formed to provide one terminal of a welding apparatus 26, cathode spacing means 28, and stop means 30.

Cathode engaging means 24 has its outermost end formed to penetrate a cylindrical cathode sleeve 32 and abut the closed end 34 thereof (see FIG. 2). The cathode should be snugly engaged by the means 24 and a proper fit may be obtained by providing the outermost end of engaging means 24 with a diameter approximately .001 inch less than the internal diameter of cathode sleeve 32.

The cathode spacing means 28 is formed to cooperate with stop means 30 for regulating the spacing of cathode 3 12 and in the embodiment shown in FIGS. 1 and 2 is com.- prised of a plurality of legs 36 which are radially spaced from cathode engaging means 24 and extend in the same direction and are substantially parallel thereto.

The stop means in this instance is a removable blade 38 which is formed to be inserted between a pair of adjacent grid electrodes. The grid electrodes most commonly used for this purpose will be the G and G however, other grid pairs may be utilized if desired.

When the stop means employed is the removable blade 38 and the grid pair is comprised of the G and the G it will be seen that the length of the legs 36 will be greater than the length of cathode engaging means 24. The difference between these two lengths will be equal to the thickness of the closed end 34 of cathode 12, plus the thickness of the emissive material thereon, plus the desired spacing between cathode and G plus the thickness of the closed end 40 of the G plus the spacing between the G and G minus the thickness of the removable blade being used.

In operation, an operator will position a cathode 12 on cathode engaging means 24. The removable blade 38 will be inserted between the appropriate pair of grid electrodes on a preassembled gun and the gun will be advanced toward the cathode. The operator will thread the cathode into the aperture provided therefor in cathode eyelet 14 and continue to advance the gun toward the cathode until the legs 36 of cathode spacing means 28 come in contact with removable blade 38. When contact occurs the cathode-to-grid spacing will be proper and the cathode will be fixed in this position. Since the cathode engaging means 24 is formed to provide one terminal of a welding apparatus attachment may be accomplished by contacting the cathode eyelet 14 with a second terminal 42 of the welding apparatus and forming a spot weld. This effectively bonds the cathode to the cathode eyelet and permanently fixes the cathode-to-grid spacing. While it is obvious that any number of welds may be used, it has been found that two welds approximately 120 apart are satisfactory.

Utilization of a jig of this type has enhanced the assembly techniques of electron gun mounts and improved the consistency in cut-off voltages, all at a reduced cost of manufacture.

In FIG. 3 is illustrated another embodiment of the invention. The jig here shown has cathode spacing means 44 comprised of legs 46 and stop means 48. The bottom surface 50 of cathode eyelet support 16 functions as the stop means and the legs 46 have a length shorter than the length of cathode engaging means 24.

Referring to FIG. 4 the jig shown therein utilizes the interior surface of the closed end 40 of the G as the stop means and has the length of the legs 52 of cathode spacing means 54 formed accordingly. In this instance it will be necessary to form appropriate passages 56 in support eyelet 16 and these may be in the form of apertures or slots.

A still further embodiment is shown in FIG. and wherein the length of legs 58 of cathode spacing means 60 and the length of cathode engaging means 24 are equal. Projection 62 in the form of an annulus on the inside surface of the G is formed to provide the required spacing distance and here has a length equal to the desired spacing, plus the thickness of the emissive material, plus the thickness of closed end 34 of cathode 12.

There has thus been provided by this invention new and novel assembly techniques and jig structures for the manufacture of electron gun mounts which represent a distinct advance in the art.

While there have been shown and described what are at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.

What is claimed is:

1. A jig for assembling and spacing a cathode relative to a grid in a cathode ray tube electron gun mount where said mount comprises at least one electron gun having a plurality of grid electrodes and a cathode support formed to receive a cathode, said jig comprising: longitudinally extending cathode engaging means having a given length; longitudinally extending cathode spacing means parallelly arrayed with said cathode engaging means and radially spaced therefrom and having a length larger than said given length; and stop means formed to engage said spacing means.

2. A jig according to claim 1 wherein said stop means is said cathode support.

3. A jig according to claim 1 wherein said stop means is the interior surface of said grid adjacent said cathode support.

4. A jig according to claim 1 wherein said stop means is an annular projection formed on the interior surface of said grid adjacent said cathode support.

5. A jig for assembling and spacing a cathode relative to a grid in a cathode ray tube electron gun mount where said mount comprises at least one gun having a plurality of selectively spaced apart, axially aligned grid electrodes and a cathode support formed to receive a cathode spaced from one of said grid electrodes and axially aligned therewith; said jig comprising: longitudinally extending cathode engaging means having a given length; longitudinally extending cathode spacing means parallelly arrayed with said cathode engaging means and radially spaced therefrom and having a length larger than said given length; and stop means formed to engage said spacing means.

6. A jig for assembling and spacing a cathode relative to a grid in a cathode ray tube electron gun mount where said mount comprises at least one gun having a plurality of selectively spaced apart, axially aligned grid electrodes and a cathode support formed to receive a cathode spaced from one of said grid electrodes and axially aligned therewith; said jig comprising: longitudinally extending cathode engaging means; longitudinally extending cathode spacing means parallelly arrayed with said cathode engaging means and radially spaced therefrom; and stop means formed to cooperate with said spacing means to determine the depth of penetration of said cathode in said cathode support.

7. A jig for assembling and spacing a cathode relative to a grid in a cathode ray tube electron gun mount where said mount comprises at least one gun having a plurality of selectively spaced apart, axially aligned grid electrodes and a cathode support formed to receive a cathode spaced from one of said grids and axially aligned therewith; said jig comprising: longitudinally extending cathode engaging means having a given length and being formed to releasably engage said cathode by an internal surface thereof, said means being further formed to provide a welding terminal; longitudinally extending cathode spacing means parallelly arrayed with said cathode engaging means and radially spaced therefrom and having a length greater than said given length; removable stop means positioned between two of said electrodes formed to engage said spacing means; and a second welding electrode formed to contact said cathode support after said cathode is positioned therein whereby securement of said cathode in a desired position is achieved.

References Cited UNITED STATES PATENTS 1,456,506 5/1923 Leveridge 29203 2,226,496 12/1940 Jacocks 29-468 2,756,709 7/1956 Coonrod 29-203 JOHN F. CAMPBELL, Primary Examiner.

THOMAS H. EAGER, Examiner. 

1. A JIG FOR ASSEMBLING AND SPACING A CATHODE RELATIVE TO A GRID IN A CATHODE RAY TUBE ELECTRON GUN MOUNT WHERE SAID MOUNT COMPRISES AT LEAST ONE ELECTRON GUN HAVING A PLURALITY OF GRID ELECTRODES AND A CATHODE SUPPORT FORMED TO RECEIVE A CATHODE, SAID JIG COMPRISING: LONGITUDINALLY EXTENDING CATHODE ENGAGING MEANS HAVING A GIVEN LENGTH; LONGITUDINALLY EXTENDING CATHODE SPACING MEANS PARALLELLY ARRAYED WITH SAID CATHODE ENGAGING MEANS AND RADIALLY SPACED THEREFRON AND HAVING A LENGTH LARGER THAN SAID GIVEN LENGTH; AND STOP MEANS FORMED TO ENGAGE SAID SPACING MEANS. 